The present invention relates to a small push switch used in various electronic appliances.
In the recent trend of smaller size and higher quality for electronic appliances, push switches and other electronic components are desired to be small, thin, and to generate clear handling feeling. A push switch having a longer operation stroke is demanded.
A configuration of a conventional push switch disclosed in Japanese Laid-open Patent No.3-214519 will be explained, referring to FIG. 14 and FIG. 15.
FIG. 14 is a front sectional view of a conventional push switch 5. In the bottom of a switch case 1 of molded resin box, two outside fixed contacts 2 coupled to a connection terminal 2A and a central fixed contact 3 coupled to a connection terminal 3A are fixed by insert molding. A movable contact 4 of elastic thin metal is disposed on the two outside fixed contact points 2.
The movable contact point 4 is made of elastic thin metal plate, and includes a ring-shaped periphery 4C and a tongue 4A extending from the periphery 4C toward its center. The tongue 4A is folded in an upward slope at a junction 4B with the periphery 4C. The periphery 4C of the movable contact 4 is disposed on the outside fixed contacts 2 to contact with the contacts 2 electrically. The tongue 4A in the center faces the central fixed contact 3 in this arrangement, providing a switch contact.
An elastic element 6 is made of rubber or other elastic material, and has a columnar bar section 6B at its upper part, and a thin conical section 6D at its lower part. A drooping section 6C projecting downward from a inside central part of the conical section 6D faces the tongue 4A of the movable contact 4 at a certain gap. An outer lower end 6A of the conical section 6D is disposed on the top of the periphery 4C of the movable contact 4.
An operation element 7 is disposed on the bar section 6B. The periphery of a lower part 7A of the operation element 7 is regulated by the inner periphery of a wall 1A of the switch case 1, thus allowing the operation element 7 to move up and down without inclination.
Two protrusions 7B on the periphery are engaged with upper and lower grooves 1B provided in the inner periphery of the wall 1A of the switch case 1, respectively. The operation element 7 is locked so as not to rotate or slip out upward. A protrusion 7C projecting upward from the switch case 1 is an operation part.
An operation of the push switch 5 will be explained below.
The protrusion 7C of the operation element 7 is pushed during the switch being turned off as shown in FIG. 14, and then, the operation element 7 pushes the elastic element 6 in the switch case 1. This operation deforms the conical section 6D of the elastic element 6, and generates a clear click feel at the time of the deformation. Simultaneously, the drooping section 6C of the elastic element 6 pushes down the tongue 4A into the center of the movable contact 4, and the lower side of the tongue 4A contacts with the central fixed contact 3. And the outside fixed contacts 2 and the central fixed contact point 3, that is, the two connection terminals 2A and 3A then conduct with each other.
Then, when a pushing force to the operation element 7 is removed, the elastic element 6 and movable contact 4 return to an initial state with their own elastic restoring force, and the two connection terminals 2A and 3A opens again.
The push switch 5 installed in an electronic appliance will be explained. FIG. 15 is a front view of a conventional push switch installed in an electronic appliance. The push switch 5 is disposed on a wiring board 8 with the connection terminals 2A and 3A connected electrically at the lower side by, e.g. soldering, and is placed immediately beneath an operation button 9 fitted to a case 10 of the appliance corresponding to the position of the operation element 7.
The interval between the lower side of the operation button 9 and the upper side of the wiring board 8 is determined according to the height of the push switch 5.
In the conventional push switch 5, however, due to fluctuations of components and their combination in the electronic appliance including the switch, or to an installing state of the push switch 5, it is difficult to set the interval between the lower side of the operation button 9 and the upper side of the wiring board 8 to be the height of the push switch 5. If the interval is too wide, a gap between the operation button 9 and the upper side of the push switch 5 makes the operation button 9 loose. If the interval is too narrow, on the other hand, the operation button slightly pushes the operation element 7 of the push switch 5, and this makes the sensation of manipulation of the push switch 5 dull.
The push switch can absorb fluctuations of components and their combination of an electronic appliance, and is prevented from looseness in an operation button of the electronic appliance including the switch, thus maintaining a clear manipulation feeling.